This will allow you generate a filter list based on live registry data.
(You can also use a regular 'whois' client against filtergen.dan.me.uk to get the same output)

Options:	Enable Debug Mode Generate IPv6 Filter Generate cisco juniper force10 mikrotik prefix-list called       Permit up-to prefix size: / (CIDR size, e.g. 24 or 64)
Data Source:	RIPE RADB APNIC
AS-SET to Query:

Output from Filter List Generator:

%
% Filter List Generator
% Copyright(c) 2018, Daniel Austin MBCS
%
% usage:
%   [-D] [-6] [-RIPE | -RADB | -APNIC] [-f filtername -t filtertype [-upto N]] as-set
%
% -D for DEBUG mode (shows working calculations)
% -6 for IPv6 filter generation
% -RIPE for whois.ripe.net lookups
% -RADB for whois.radb.net lookups
% -APNIC for whois.apnic.net lookups
% -f will generate a cisco-style filterlist called 'filtername' (use -t filtertype as follows)
%      cisco (default)
%      juniper (basic support)
%      force10
%      mikrotik
% Additionally, if using -f/-t you may specify -upto N where N is the prefix size to permit up-to
%
% Using whois.radb.net for lookups
% Generating filter list for 'AS14618'
66.7.64.0/19
63.92.12.0/22
63.238.12.0/22
63.238.16.0/23
208.47.248.0/23
50.19.128.0/17
107.20.0.0/16
107.22.0.0/16
107.21.0.0/18
54.212.0.0/16
54.240.24.0/22
54.253.128.0/17
54.221.0.0/16
54.211.0.0/16
54.213.0.0/16
54.215.192.0/18
54.219.0.0/17
54.202.0.0/15
23.20.0.0/15
107.23.0.0/17
23.22.0.0/15
54.200.0.0/15
54.229.128.0/17
54.207.0.0/17
54.238.128.0/17
54.207.128.0/17
54.204.0.0/15
54.206.0.0/17
54.220.0.0/16
54.219.128.0/18
54.199.0.0/17
54.194.0.0/16
54.255.0.0/17
54.219.192.0/18
54.196.0.0/15
54.193.0.0/17
54.255.128.0/17
54.84.0.0/15
54.72.0.0/16
54.186.0.0/15
54.242.0.0/15
54.240.8.0/21
54.184.0.0/15
54.195.0.0/16
54.193.128.0/17
54.198.0.0/16
54.80.0.0/14
54.206.128.0/17
54.199.128.0/17
54.73.0.0/16
54.86.0.0/16
54.188.0.0/15
216.182.224.0/21
216.182.224.0/20
216.182.232.0/21
67.202.0.0/18
72.44.32.0/19
75.101.128.0/17
54.234.0.0/15
107.23.128.0/17
50.16.245.0/24
54.236.0.0/18
174.129.0.0/16
107.21.64.0/18
107.21.128.0/17
54.237.0.0/16
54.228.0.0/16
54.232.192.0/18
54.249.64.0/18
54.241.192.0/18
54.241.160.0/19
54.249.128.0/17
54.244.128.0/17
54.236.64.0/18
54.236.128.0/17
54.224.0.0/15
204.236.224.0/19
204.236.192.0/18
184.73.0.0/16
184.72.128.0/17
54.253.0.0/17
54.215.0.0/17
54.244.64.0/18
54.214.0.0/17
54.250.0.0/17
54.250.128.0/18
184.72.64.0/19
54.216.0.0/15
54.208.0.0/15
54.226.0.0/15
54.229.0.0/17
54.232.128.0/18
54.215.128.0/18
54.214.128.0/17
54.240.16.0/24
184.72.96.0/19
54.254.0.0/17
54.218.0.0/17
54.218.128.0/17
54.250.192.0/18
54.254.128.0/17
54.238.0.0/17
50.16.252.0/22
50.17.0.0/16
50.19.0.0/17
54.156.0.0/14
54.151.0.0/17
54.93.32.0/19
54.93.64.0/18
54.93.0.0/19
52.0.0.0/15
54.93.128.0/17
52.64.0.0/17
52.8.0.0/16
185.48.120.0/22
54.95.0.0/17
54.79.0.0/17
54.94.0.0/17
54.87.0.0/16
54.76.0.0/15
52.10.0.0/15
54.152.0.0/16
54.153.0.0/17
54.153.128.0/17
52.16.0.0/15
52.74.0.0/16
54.183.0.0/17
54.176.0.0/15
54.74.0.0/15
54.95.128.0/17
54.89.0.0/16
54.90.0.0/15
54.191.0.0/16
54.233.64.0/18
54.233.128.0/17
52.12.0.0/15
52.28.0.0/16
54.190.0.0/16
54.88.0.0/16
54.179.128.0/18
54.94.128.0/18
54.210.0.0/16
52.68.0.0/15
52.4.0.0/14
52.24.0.0/14
54.92.0.0/17
54.64.0.0/15
54.183.128.0/17
54.166.0.0/15
54.92.128.0/17
54.164.0.0/15
52.76.0.0/17
54.168.0.0/16
54.68.0.0/15
54.70.0.0/15
54.78.0.0/16
54.179.192.0/18
54.66.0.0/17
54.160.0.0/14
52.2.0.0/15
52.95.52.0/22
54.169.0.0/17
52.18.0.0/15
54.66.128.0/17
54.172.0.0/15
54.171.0.0/16
54.170.0.0/16
54.67.0.0/17
54.174.0.0/15
54.169.128.0/17
54.94.192.0/18
54.144.0.0/14
54.148.0.0/15
54.151.128.0/17
54.150.0.0/16
54.93.0.0/16
54.79.128.0/17
54.154.0.0/16
54.155.0.0/16
52.20.0.0/14
52.95.241.0/24
52.95.243.0/24
52.95.242.0/24
52.95.244.0/24
52.95.245.0/24
52.95.240.0/24
52.95.246.0/24
52.95.247.0/24
52.64.128.0/17
52.29.0.0/16
52.88.0.0/15
52.70.0.0/15
52.72.0.0/15
52.86.0.0/15
52.90.0.0/15
52.30.0.0/15
52.95.248.0/24
52.32.0.0/14
52.76.128.0/17
52.77.0.0/16
52.9.0.0/16
52.52.0.0/15
52.192.0.0/15
23.20.0.0/14
50.16.0.0/16
50.16.0.0/14
50.112.0.0/16
52.65.0.0/16
52.62.0.0/15
52.48.0.0/14
52.58.0.0/15
52.95.30.0/23
52.13.252.0/23
52.200.0.0/13
52.44.0.0/15
52.54.0.0/15
54.240.30.0/23
54.240.32.0/20
54.240.48.0/23
34.192.0.0/12
34.224.0.0/12
35.168.0.0/13
35.153.0.0/16
18.204.0.0/14
18.208.0.0/13
18.232.0.0/14
216.182.232.0/22
216.182.238.0/23
100.24.0.0/13
76.223.191.0/24
3.80.0.0/12
130.137.186.0/24
81.90.143.0/24
% end of filter list for 'AS14618' (233 prefixes found) 
% took 0.40 secs for query (0.29 secs of connection time)
% used 1 connections -- 698 lines of whois data parsed